I'm making a very simple gizmo to control one brake with two levers. My original goal was to replace the current parking brake setup on my touring bent, which is a third V-brake on the rear wheel controlled by a thumb shifter, by something lighter and more elegant, in the form of the regular brake controlled by the regular brake lever as well as the thumb shifter. To do that, I've designed a simple device that works pretty much like a cyclocross lever, but controlled by another cable, i.e. something that pulls the main cable line's sleeve apart when the secondary cable is pulled.
I'm about to finish the thing. It's composed of 3 simple parts and a screw, and should weigh 15/20g. Next week, I have an opportunity to have some time on the workshop's CNC lathe, and so I'm trying to figure out if there's interest for such a gizmo : I'm thinking of tourers who might need a parking brake of course, but also tandemists who might want to double the controls for the brakes and/or derailleurs, so the stocker can also control most of the bike, and other goofball projects. If there's interest, I could perhaps get the lathe to spew out 10 sets of parts, and so it'd be worth buying a rod of stainless steel to make them out of, instead of the crummy carbon steel I'm using for my prototype.
So, would you want such a device? If I'm the only one, I'll stick with mine. If there's enough people interested, I'll sell them at cost, i.e. the price of the stainless steel + shipping, and I'll ask those who try it out to act as guinea pigs and report on its real-life usability. At any rate, if anybody wants the plan, I'll happily post it.
The main brake line runs in the middle, and the secondary brake control line on top. When the latter is pulled, the main brake line's sleeve is pulled apart, working the brake like the main lever would:
The nice thing is, if the secondary line is connected to a derailleur thumb shifter (i.e. to act as a parking brake), a hard squeeze of the main lever yanks the secondary cable hard enough to flip the thumbshifter and release the parking brake.
Net weight: 56g, a bit more than I expected, but then I didn't try to make it light. Still, it's better than a V-brake. I'll mount the thing permanently on the bike when the weather gets better and I'll snap more pics.